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A/P > Lecture 10/25 & 10/28 > Flashcards

Lecture 10/25 & 10/28 Flashcards

Test 4

1
Q

T/F: purkinje fibers doesn’t have a lot of fast Na+ channels

A

F

Has lots of them

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2
Q

Repolarization is done _______ in the epicardium in the ventricles. The endocardium _________ to repolarize.

A

quicker/sooner

takes longer

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3
Q

Describe an Atrial muscle AP

A

Visually between a slow (SA) and fast (Ventricles) AP

Phase 0 is straught up like ventricles
AP is short like SA

This is d/t atria only contracting for a short period of time and not having to pump against a high resistance because the atria walls are thin

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4
Q

T/F: the heart uses neurotransmitters to permit AP

A

F

Gap junctions

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5
Q

Whats the easiest thing to go through the gap junction? What all can go through there?

A

Na+

Ca++ – bigger, therefore slower –> slower for AP

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6
Q

What is a con of gap junctions in the heart?

A

They are bidirectional

If there’s an atomic pacemaker generating AP in parts of the heart that it shouldn’t be, that AP can travel forward/backwards to a cell that isnt finished resetting and cause life threatening arrthymias (Ex. T-on-T; R-on-T)

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7
Q

What helps prevent re-entry rhythms?

A

Absolute refractory period

If an AP hits the cell while its in absolute refractory period, it wont generate an AP

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8
Q

What happens if an AP hits a cell while it’s in the relative refractory period?

A

Odd AP –> heart wont pump right

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9
Q

Which leads look at electrical current in the frontal plane?

A

3-leads
augmented leads

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10
Q

Frontal plane is also called ________

A

coronal plane

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11
Q

In 3 leads: Describe the leads that are on each limb

A

R arm: 2 neg

L foot: 2 positives

L arm: 1 neg/1pos

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12
Q

The 3 leads setup forms a _____ degree triangle

A

60

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13
Q

In a 3-Lead set up: Describe lead/electrode placement

A

Lead I: Horizontal
Positive L arm; Negative R arm

Lead II: Aimed toward L foot
Positive L foot; Negative R arm

Lead III: Aimed toward R foot
Positive L foot; Negative L arm

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14
Q

In 3-lead, which lead has the best view and why?

A

Lead II

Lead II (+) lead is aimed at L foot at 60 degrees which is almost the same as the mean electrical axis of 59 degrees

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15
Q

Who is Einthoven?

A

Dutch scientist from Europe

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16
Q

What are the 3 things we need for an EKG to work?

A

Leads
Recorder
Amplifier (makes it easier for recorder to pick up things)

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17
Q

The mean axis is ____ and is pointed to the _______

A

59 degrees

L foot

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18
Q

Which lead is similar to the mean axis?

A

Lead II

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19
Q

What is Right deviation?

A

Anything that shifts the heart greater than 59 degrees to the right.

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20
Q

What is a left deviation?

A

Anything that shifts the heart less than 59 degrees to the left.

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21
Q

What are some conditions that can make your heart deviate?

A

BBB
Big lungs from COPD

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22
Q

How does breathing effect your mean axis?

A

Deep breath in = shift axis to R

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23
Q

Postive angles are ________. Negative angles are ___________.

A

Clockwise

Counterclockwise

Ex) 60 degrees = -300 degrees

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24
Q

Describe the walls of the ventricles

A

R wall thinner than L wall

R wall only has to pump against resistance of pulmonary circulation

25
Q

How does depolarization work in the ventricles?

A

L BB –> R BB –> L & R Ventricles endocardium –> to epicardium

26
Q

If we could see atria repolarization, what would it be?

A

Negative deflection

27
Q

Describe atria depolarization

A

Similar to ventricle depolarization

Toward L foot –> positive deflection lead II

28
Q

What atria depolarizes fastest?

A

R atria

29
Q

Describe Einthoven’s Deconstructed triangle

A

pulled apart and able to plot on a graph and intersect at a midpoint

Lead I: 0 degrees + / 180 (-)

Lead II: 60 (+) / 240 (-)

Lead III: 120 (+) / 300 (-)

30
Q

What is Einthoven’s Law?

A

Net deflection in:

Lead I + Lead III = Lead II

31
Q

How does lead I & lead III compare to lead II?

A

In a healthy heart, deflections will be smaller

32
Q

If I need something outside of a frontal view, I need _________ leads

A

Precordial

33
Q

When do you not see a deflection in lead I?

A

When this mean axis is perpendicular to lead I
Straight up/down

34
Q

How do you find the net deflection in a QRS?

A
  1. Draw a line from the beginning of P wave across EKG
  2. Anything above that in QRS is positive deflection; below is negative
  3. Subtract the negative deflection from positive deflection.
35
Q

If the mean axis is 60, what can we assume?

A

The net deflection in lead I & III are equal (equal vectors)

36
Q

What does augmented leads view?

A

frontal electrical current (coronal)

37
Q

aV____ means…

A

lowercase a = augmented
V = voltage
letter after is the location of the (+) electrode

38
Q

In augmented leads: describe lead/electrode placement

A

aVR: R arm (+) / average LL/LA (-)
Majority deflections negative, lead used the least
-points to R arm

aVF: L foot (+) / average RA/LA (-)
-points straight down

aVL: L arm (+) / average RA/LL (-)
-points to L arm

39
Q

What angle are the augmented leads?

A

aVR: 210 degrees

aVL: -30

aVF: +90

40
Q

Which lead dont we use much? why?

A

aVR

(+) electrode at R arm; deflection almost always inverted

41
Q

Which augmented leads are we more likely to see normal deflections in?

A

aVL and aVF

positive electrodes on the right and bottom so able to measure electricity from R –> L

42
Q

Which leads are closest to chest? What does this mean?

A

Precordial Chest leads

Bigger deflections overall

43
Q

How many precordial leads are there? How would you describe them?

A

6

They are all positive leads

V1-2: sternum leads
V3-4: anterior leads
V5-6: lateral leads

44
Q

Where do you place the Precordial leads?

A

V1: R sternum/septum 4th ICS
V2: L sternum/septum 4th ICS
V3: between 2&4
V4-6: L lateral 5th ICS

45
Q

Where is the negative electrode in precordial leads?

A

The average (-) in the standard 3 leads on RA/LA/LL

46
Q

What are you able to see in V1? How does this show up in an EKG?

A

Top R of heart

Large (-) deflection for QRS; inverted P-wave

47
Q

Describe the V2 lead

A

QRS probably negative (-)

This lead in the middle of the heart
Used most to see if posterior/anterior injury

48
Q

What lead is used to Dx posterior/anterior injuries?

A

V2

49
Q

If current is moving toward V2 it is an _________ injury, and will show up as a ______ deflection

A

Posterior

positive

50
Q

If current is moving away from V2 it is an _________ injury, and will show up as a _______ deflection

A

anterior

negative

51
Q

Which lead has the biggest deflections overall? Why?

A

V4

Closest to the heart & close to 59 degree mean axis

52
Q

V5 & V6 are progressively _______ than V4

A

smaller

further lateral on chest wall

53
Q

What lead will not have an S- wave? Why?

A

Lead I

At the end of depolarization when the L lateral piece of the ventricle is depolarizing, the vector is now pointing more toward the (+) electrode in lead I

54
Q

What lead will not have a Q-wave?

A

Lead III

55
Q

T/F: When a ventricle is depolarized you will have a small vector

A

F

There is no current UNLESS THERE IS AN INJURY
You will have no vector & no current & all meters should read 0

56
Q

What does a vector tell you?

A
  1. The angle tell you which way the current is going
    The opposite direction of an injury as well
  2. The size of the vector tells you how much electrical current is involved
57
Q

What is a normal QT interval?

A

0.25 - 0.35 secs

58
Q

What is another name for 3-leads?

A

Bipolar Leads

A/P (26 decks)

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